In recent years the trend in detergent compositions has been towards reducing or eliminating phosphate builders. The replacement of sodium tripolyphosphate as a builder in powdered detergent compositions by crystalline sodium aluminosilicate (zeolite) and/or by sodium carbonate has led to a number of difficulties with the structure and properties of the powder. One such problem that has been encountered is the tendency to dispense less well in front-loading automatic washing machines than do similar phosphate-built powders: a higher proportion of the powder dosed into the machine is left behind in the dispenser, leading to product wastage and clogging. This problem is especially marked at the low wash temperatures now preferred for energy-saving reasons.
Another problem observed with zeolite-built powders is a relatively high level of insoluble matter deposited on the machine surfaces or on the washed fabrics.
Both these problems have been exacerbated by the recent trend in the detergents industry towards higher bulk density powders.
We have now found that high bulk density powders having improved flow and dispensing properties and low levels of insoluble matter can be prepared by coating the particles of a detergent base powder with a relatively large amount of finely divided zeolite powder, and then spraying on a liquid binder comprising nonionic surfactant.